1. Field of the Invention
The present invention relates to a novel integrated process for the environmentally benign use of grains and renewable materials to produce “clean beef” (or milk), fuel ethanol for motor fuel purposes, and bio-gas/bio-fertilizer from animal wastes and other residual streams.
2. Background of the Prior Art
Agriculture in general, and the livestock feeding industry in particular, face increasing pressures which pose challenges to traditional methods of doing business, and offer opportunities to those with improved methods. Trends in the marketplace have created a demand for beef and diary products that are high quality, and verifiably safe. Environmental authorities at both the national and local levels are imposing requirements on concentrated animal feeding operations (CAFOs) to ensure that odor and environmental contamination are substantially reduced from current levels. Cost effective methods of converting animal wastes into marketable fuels and products are needed. Public policy is encouraging substantial expansion in fuel ethanol production but conventional ethanol technology relies heavily on purchased natural gas to generate steam for operations, and high natural gas costs have stifled capital investment in new plants. To the greatest extent possible, all of these methods and products should be generally “sustainable” (e.g., renewable) and environmentally friendly.
In conventional practice, beef cattle are normally fed 22 pounds of dry matter equivalent per day with as much as a 50% moisture content for a total feed weight of approximately 44 pounds per day. The moisture content represents a portion of the animal's total daily water intake. Cattle on average convert 6.5 pounds of feed into one pound of body weight gain. If the animal gains 3.5 pounds of weight per day and requires 6.5 pounds of feed per pound of gain, it must consume 22.75 pounds of dry matter feed per day. This diet not only allows for weight gain but provides the energy to sustain the animal in good health. Dairy cows, which like beef cattle, are ruminant animals, require approximately 50 pounds of dry matter intake per day to support milk production. Approximately 70% of the animal's dry matter feed ration is digestible. The non-digestible and water portions are passed as manure and urine which in conventional practice are typically dumped onto the ground. The pens are then occasionally cleaned by scraping the manure and dirt mixture into wind row piles where it sun-dries. The mixture is eventually field applied, sold as fertilizer or disposed of in some fashion. Due to growing environmental concerns, however, manure management is rapidly becoming one of the most critical functions in CAFOs.
Modern feedyards are designed to catch the water runoff from cattle pens in special drain basins or pits which are often aerated to introduce more oxygen into them. The water will evaporate as new runoff continuously refills the pits. They are designed to normally handle up to a 25-year rain runoff. However, in just the last 25 years, there have been not only 25-year rains but a 50, 100 and even a 300-year rain in the Midwest. These heavy rains can, and do, overwhelm the feedyards' ability to manage the pen drainage systems.
Dairies, although historically smaller, encounter similar manure pollution challenges.
Since the early 1990's, many states and the federal government have begun to review the public policies regulating CAFOs. Many complaints have been received from environmentalists, naturalists, fishermen and neighbors regarding the untreated contamination resulting from the feedyards. The sheer volume of cattle waste (12 times that of one adult human per day) is cause for considerable concern. Whereas human waste is treated in sewage disposal plants, septic tanks or by other approved methods, conventionally, cattle waste is not so treated.
The United States has a population of approximately 275 million people and raises approximately 100 million cattle, of which over 32 million are brought together in CAFOs. If each adult animal produces 12 times as much waste as an adult human being, the United States is producing the animal waste-equivalent of a nation of 385 million people, just in feedyards. The U.S. has approximately 10 million head of dairy cows on feed annually, which produce the waste equivalent of 14 million beef cattle.
Consequently, ruminant animals, primarily beef cattle and dairy cows, are posing a substantial threat to the environment, despite their importance as human food sources. Cattle on farms and ranches average approximately one animal for each 12 acres or about one animal per 500,000 square feet, whereas, in a confined feedyard operation, one animal has an average of 250 square feet. This animal density concentrates the manure into very small areas and local ecosystems are thereby jeopardized.
CAFOs larger than 1,000 beef animal units (equivalent to 700 dairy cows) are the point source for numerous real and perceived environmental problems: water contamination, airborne particulates, objectionable odors, fly and insect infestations, nitrogen and phosphorus buildup in the soil and major fish kills in rivers and streams. In its Dec. 15, 2002 final rule (40 CFR Parts 9, 122 and 412), the U.S. Environmental Protection Agency (EPA) stated that its new regulations would ensure “that an estimated 15,500 CAFOs effectively manage the 300 million tons of manure that they produce annually.” The troublesome greenhouse gas (GHG) emissions of methane is another major environmental problem. Worldwide, cattle are the single largest animal source of methane release into the environment (methane is 22 times more potent than CO2 as a greenhouse gas).
Most states require freshly applied raw animal manure to be incorporated into the soil at prescribed depths and within 12 hours of manure application. This is the most “economic” use of feedyard manure today. Feedyards that recover manure but do not keep it separated and free from dirt contamination, will normally sell the pen scrapings in a dry form. However, this method is more labor intensive and requires additional equipment and real estate for wind row drying. At this point, the waste byproduct can pollute the surrounding environment if washed away during wet periods and the opportunity for odor and insect problems increases.
Another major environmental concern caused by CAFOs is the build-up of nitrogen and phosphorus in the soil where manure is applied or disposed of. This build-up comes from the long-term consumption, and then concentration, of feed grain in the relatively small area encompassed by a CAFO. For example, a typical feedyard will consume approximately 20 pounds of corn per animal per day. In a 25,000 head feedyard that is full with year-round operation, this amounts to approximately 3,250,000 bushels of corn per year.
In the corn belt of the upper Midwest each acre of corn receives approximately 135 pounds of nitrogen per acre and will yield approximately 130 bushels of corn per acre. When the mature corn is harvested only the seed is saved and the plant is reincorporated into the soil for nutritional enrichment. The 130 bushels of seed corn taken from the acre contain most of the nitrogen and phosphorus which is then transported to the cattle feedyard for feed rations. If a typical 25,000 head location utilizes 3.25 million bushels per year and the average production is 130 bushels per acre, the feedyard will require all of the output from 25,000 acres of corn.
If a conventional 25,000 head feedyard is built on approximately 250 acres of land, this means the nitrogen and phosphorus is taken from 25,000 acres of corn and ends up on 250 acres of feedlot—a concentration of 100-fold. During the feeding cycle, cattle use approximately one-half of the nitrogen in the corn for body growth by converting it to protein. Thus, this portion of the nitrogen leaves the feedyard as meat. Taking into account conversion factors, on balance, 66% of the nitrogen and 100% of the phosphorus is left behind. The manure management of the feedyard must then move these compounds back to local farm fields as replacement fertilizer needed for next year's crop, under EPA's new rules, with upper limits at the crop's “agronomic uptake levels.”
If the feedyard does not collect and apply these compounds properly to the land, it will end up in the environment. Large portions of the nitrogen and phosphorus are typically transported off site via water runoff, airborne particulates, manure removal or disposal, etc. The principal environmental threat is that large volumes of nitrogen and phosphorus enter the water system, as in the widely reported instances of runoff from Midwestern states like Iowa and Illinois into the Mississippi River, and ultimate deposit in heavy concentrations in the Gulf of Mexico and elsewhere, causing immense “dead zones” which cause the death of shrimp and other fish due to oxygen depletion.
While anaerobic digestion of manure has been known for centuries, it has never been practiced on a large scale basis in cattle feedlots due to poor economics, inability to prevent manure contamination by soil and water and limited outlets for the bio-methane. It's practice by dairies has been limited due to marginal economics, largely driven by parasitic heat loss, and low revenue from biogas-generated electricity sales, as dairies have no economically useful demand for low pressure steam.
It is clear that a new approach to CAFOs is needed in order to address the concerns of environmental regulators, consumers, and the economic pressures facing the industry itself.
Recent outbreaks of E. Coli-contaminated meat, and growing consumer demand for “clean” beef have combined to put significant pressure on livestock producers, feedlot operators, and meat packers. In the U.S. conventional feeding methods rely upon heavy use of anabolic steroids, antibiotics, and other artificial practices to promote animal weight gain. However, the U.S. Food and Drug Administration (FDA) has expressed growing concern over the threat posed by excessive antibiotics use in animal feeding, which experts now link to the proliferation of drug-resistant bacteria, and increasing humans' vulnerability to untreatable infections.
Moreover, food safety officials have expressed growing concern about the long-term health effects of eating beef which contains high levels of antibiotics and growth hormones, and many nations prohibit the importation of U.S. beef that contains growth-enhancing steroids, hormones, and other “artificial” additives. Consequently, consumer export for U.S. beef has declined in recent years.
A recent Presidential Executive Order set a national goal of tripling the production and use of bio-fuels by the year 2010, in large part due to the need to achieve substantial reductions in emissions of greenhouse gases such as carbon dioxide (CO2) and methane. Primary sources of CO2 are fossil fuel combustion, and a primary source of methane emissions is cattle flatulence and manure. Renewable bio-fuels such as ethanol and bio-gas using conventional methods are not cost competitive with fossil fuels, and new approaches are needed if the production goals are to be met. One of the most capital- and energy-intensive sections of modern-day ethanol plants is the spent mash (protein co-product) drying and handling section. The protein co-product is valued as an effective feed ingredient for ruminant animals (cattle and dairy cows), but in traditional practice must be dried before it can be transported and stored. Eliminating this requirement would result in substantial capital, energy and operating cost savings in ethanol production. In addition, since Sep. 11, 2001, homeland security objectives dictate the need for dispersed and decentralized forms of energy production that can operate independently of conventional refineries, pipelines and even the electricity grid.
The invention as described and claimed in U.S. Pat. No. 6,355,456 addressed many of the foregoing problems by integrating an ethanol production unit with a cattle feedlot (or dairies) and thereby rationalized both the disposal of residue from the ethanol units and anaerobic digestion of ruminant animal waste. However, that prior invention still required some purchase of natural gas from an external source to supply the energy necessary for production of process steam, heat for operation of the ethanol units and, accordingly, the integrated bio-refinery (IBR) of the prior invention was not a wholly self-contained operation. Ammonia tended to build-up in the digester system, and the production of bio-gas from the digesters is significantly reduced by the ammonia build-up. The design of the previous invention was also limited in that it required a minimum number of cattle in the feed lot in order to justify digester operation. Another limitation of the prior invention as the high phosphorus and nitrogen content of the filtrate from the digester or the so-called “liquid fertilizer.”